EP 0 044 291 A1 discloses a device with an oscillating continuous casting mold for determining the frictional forces prevailing between the side walls of the mold and the surface of a billet held therein. The mold is connected to an acceleration sensor, and a force measuring device is provided on the support of the mold to measure the forces transmitted from the mold to the support. The acceleration sensor and the force measuring device are connected to each other by an electric subtraction circuit. Analysis of the difference between the driving force signal and the acceleration signal provides a standard measure for the friction between the billet and the mold. This method is based on the idea that the sum of all forces acting on the mold equals zero.
A disadvantage of the known process is the use of malfunction-prone acceleration sensors in the aggressive environment near the mold. Furthermore, friction within the drive is not taken into account. Moreover, the known process is limited to conventional molds. Particularly in the case of molds mounted in spring assemblies ("resonance molds"), significant spring forces occur, which must be considered in the forces balance of the mold.
DE 27 43 579 C2 discloses a process for controlling the continuous casting of metals in which the mold is oscillated and the surface of the molten metal in the mold is covered with a protective powder of a given composition. The surface of the billet leaving the mold is first observed and the effective mold movements are registered, then compared to a predetermined spectrum of effective mold movements.
In this case, an acceleration sensor is attached to the mold of the casting machine, and the acceleration signal is processed in a data transmitting device that is not described more specifically. The process starts from the fact that friction between the billet and the mold influences the frequency spectrum of the acceleration signal. It is unclear whether the friction force is compared to frequency portions of the mold movement or of the structure-borne sound.
A disadvantage of this process is the long reaction time that results from the frequency analysis. Only one mean chronological value is found. Moreover, the frictional force is only determined relative to the range of change in the frequency spectrum. In addition, the acceleration sensor is arranged in the aggressive environment near the mold.